1. Field of the Invention
The present invention relates to an electromagnetic clutch for obtaining a selective connection of a rotating movement from a rotating movement source to a receiver of the rotating movement. The present invention can be suitably used for a clutch arranged between a compressor for an air conditioning device for an automobile and the crankshaft of an internal combustion engine. The present invention is, in particular, related to a decrease in the noise which is generated when a rotor and an armature contact each other due to an electromagnetic force therebetween.
2. Description of Related Art
Known is an electromagnetic clutch which has a rotor which is connected to a source of rotating movement, such as a crankshaft of an internal combustion engine, an armature which is arranged so as to be oppositely faced with the rotor, a solenoid for generating an electromagnetic force, a hub as a receiver of a rotating movement, which is connected to a compressor of an air conditioning apparatus, and plate springs for connecting the armature with the hub. A solenoid is also provided, which produces, when energized, an electromagnetic force, which causes the armature to be moved against a force of the plate springs, so that the armature contacts the rotor face to face, which causes the rotational movement from the rotor to be transmitted to the hub via the armature and the plate springs.
In the prior art construction, when the solenoid is in a de-energized condition, the armature is spaced from the rotor so that a small gap is created between the faced surfaces of the armature and the rotor. Upon the energization of the solenoid, a collision occurs between the armature and the rotor, which causes a noise to be created. Due to the fact that the armature is supported on the hub by way of the plate springs, the armature has a relatively low rigidity. As a result of the low rigidity, the collision of the armature and the rotor causes the armature to vibrate, which causes a large amount of noise to be generated. In other words, a large noise is generated when the armature is moved to be in contact with the rotor due to the energization of the solenoid.